Field of the Invention
The invention concerns a method for magnetic resonance imaging, a local coil for a magnetic resonance apparatus, and a magnetic resonance apparatus.
Description of the Prior Art
In a magnetic resonance apparatus, also referred to as a magnetic resonance tomography system, a subject to be examined, in particular the body of a patient, is normally subjected to a relatively high basic magnetic field, for example 1.5 or 3 or 7 Tesla, by the operation of a basic field magnet. In addition, gradient pulses are activated by a gradient coil unit. Radio-frequency (RF) pulses are then emitted by a suitable antenna arrangement, such as a radio-frequency antenna unit. The RF pulses serve as excitation pulses, which means that the nuclear spins of particular atoms resonantly excited by the radio-frequency pulses are tilted by a defined flip angle with respect to the magnetic field lines of the basic magnetic field. As the nuclear spins relax radio-frequency signals, so-called magnetic resonance signals, are emitted that are received by suitable radio-frequency antennas, and then processed further. Finally, the desired image data can be reconstructed from the raw data thus acquired in this manner.
For a particular measurement, a specific magnetic resonance sequence, also referred to as pulse sequence, is to be transmitted, which is composed of a series of radio-frequency pulses, in particular excitation pulses and refocusing pulses, as well as gradient pulses appropriately coordinated therewith, activated in different gradient axes along different spatial directions. Readout windows chronologically appropriate for this purpose are set, which predetermine the periods of time in which the induced magnetic resonance signals are acquired.
With such a pulse sequence, a measurement (data acquisition) by the magnetic resonance apparatus is typically carried out by the scanner of the magnetic resonance apparatus. Prior to the measurement, an adjustment of the scanner takes place, which can include, for example, setting the resonance frequency for the scanner and/or adjust shimming components by using shim settings.